Slipring assembly

ABSTRACT

A slipring assembly including male and female portions wherein said portions are comprised of a stack of dielectric wafers and dielectric annular waferlike members, respectively. The stack of wafers, or discs, forming the male portion of the assembly is provided with a plurality of spaced-apart conductive sliprings. Registered apertures in the wafers provide wiring passages, or conduits, for electrical wires which are electrically bonded to the various conductive rings on the male portion. Each annular waferlike member comprising the female portion, which concentrically encompasses the male portion, carries four gold alloy contact wires, or brushes, which contact the conductive ring on one of the wafers comprising the male portion. The four wires are placed so that four points of contact with the slipring are spaced approximately 90* apart.

United States atent [72] Inventors Albert P. Richter, Jr.;

James D. Bruner, both of Houston, Tex. [21] Ap l. Nov 871,773 [22] Filed Oct. 30, 1969 [45] Patented Oct. 19, 1971 [73] Assignee Texaco Inc.

New York, N.Y. Continuation of application Ser. No. 682,485, Nov. 13, 1967.

[5 4] SLIP-RING ASSEMBLY 3 Claims,'1l Drawing Figs.

[52] US. Cl 340/18 LD, 310/249, 310/251, 339/5, 339/8 [51] Int. Cl ..H01r 39/08, G01v 1/40 [50] Field of Search 310/249, 251; 339/5, 8; 340/18, 18 LD [5 6] References Cited UNITED STATES PATENTS 1,300,239 4/1919 Berst 310/249 1,802,957 4/1931 Ragsdale et al 310/249 2,924,800 2/1960 Scarborough 339/5 3,089,113 5/1963 Mohr 339/8 Primary ExaminerRodney D. Bennett, Jr.

Assistant Examiner-Daniel C. Kaufman Att0rneysl(. E. Kavanagh, Thomas H. Whaley and Robert J.

Sanders, Jr.

ABSTRACT: A slipring assembly including male and female portions wherein said portions are comprised of a stack of dielectric wafers and dielectric annular waferlike members, respectively. The stack of wafers, or discs, forming the male portion of the assembly is provided with a plurality of spacedapart conductive sliprings. Registered apertures in the wafers provide wiring passages, or conduits, for electrical wires which are electrically bonded to the various conductive rings on the male portion. Each annular waferlike member comprising the female portion, which concentrically encompasses the male portion, carries four gold alloy contact wires, or brushes, which contact the conductive ring on one of the wafers comprising the male portion. The four wires are placed so that four points of contact with the slipring are spaced approximately 90 apart.

PATENTEU UCH 9197! SHEET 2 OF 3 SLIP-RING" ASSEMBLY This is a continuation of application Ser. No. 682,485, filed Nov. 13, 1967.

BACKGROUND OF THE INVENTION This invention pertains, in general, to slipring assemblies; and, more particularly, to slipring assemblies which are especially suited for operation in hostile environments, such as in apparatus for logging an earth borehole while the earth borehole is being drilled.

Often while seekirig subsurface oil, gas or minerals and the drilling of an earth borehole is in progress, it is necessary to both obtain and record measurements of various parameters in situ; i.e., the detection, measurement and recording are all done in the borehole while the drilling is in progress. While drilling an earth borehole as the drill string and drill bit rotate and penetrate the various earth formations the simultaneously functioning logging equipment incorporated in the drill string is subjected to vibration. The rotary motion, among other motions, often subjects the logging equipment to violent shocks and impact forces. In addition to the high-vibration environment within the earth borehole, high temperatures also prevail; e.g., up to 100 C. The logging equipment may be incorporated in the drill string in a manner like or similar to that disclosed in the US. Pat. application, entitled Logging While Drilling System, Ser. No. 674,335 filed Oct. 10, 1967, in behalf of Albert P. Richter, Jr. and James D. Bruner. The logging equipment includes operationally sensitive elements or components which are relatively delicate, structurally; e.g., a magnetic tape-recording unit, inter alia, is included. Usually the recording unit is mounted so that it may rotate about the longitudinal axis of the drill pipe in order to prevent damage from the severe angular shocks previously mentioned. In order to carry electrical signals from various transducers to the recorder, at least one slipring assembly is necessary. See, for example, the patent application hereinbefore identified. Hence, in the hostile environment (vibration and temperature) hereinbefore mentioned, what is needed is a reliable low-noise set of sliprings. The sliprings have to be able to carry low level low-current signals in the aforementioned environment. In addition, they also have to be able to operate with either no relative motion between the male and female portions or with the portions rotating in either direction relative to each other.

Heretofore, one form of slipring assembly included a silver commutator ring, or slipring, and a spring-loaded contactor or brush made of a carbon silver mixture. Although this type of system performs satisfactorily in an environment where little or no vibration is present the noise encountered under high-vibration conditions is considerable due to the large contactor mass. In order to reduce this noise an increase of the spring tension on the contactors was increased. But this resulted in excemive wear of the contactors. Furthermore, another method used was to make the contactor out of a small diameter gold alloy wire. These contactors or brushes are usually supported from one end with electrical contact made with the commutator ring at the other end. A small radius bend was made on the contact end to increase the contact area with the ring.- Due to the fact that the contact area was small, multiple numbers of these contactor wires or brushes was used. A big difficulty'with this kind of arrangement is that the direction of relative rotation between the male and female portions of the slipring assembly always had to be the same and the wires forming the contactors or brushes had to be secured in a definite orientation. The sliprings on the male portion of the assembly could not be removed-from the whole assembly without disassembling the entire assembly because the contactor wires would have been bent in the process.

SUMMARY OF THE INVENTION One object of the invention is to provide a new and improved slipring assembly.

Another object of the invention is to provide a slipring assembly wherein the male and/or female portions thereof are able to rotate in either a clockwise or counterclockwise direction relative to each other.

Another object of the invention is to provide a slipring assembly wherein the male and female portions thereof can easily be engaged and disengaged from one another without damaging the wire brushes.

Another object of the invention is to provide a slipring assembly characterized by low noise and high stability in hightemperature and high-vibration environments.

Another object of the invention is to provide a new and improved slipring assembly which is better able to withstand the hostile environment occasioned while the drilling of an earth borehole is in progress.

Another object of the invention is to provide a slipring assembly for well-logging apparatus.

Another object of the invention is to provide a slipring assembly which, as compared with prior art assemblies, is easily and quickly maintained, repaired and reassembled.

Another object of the invention is to provide a new and improved slipring asembly which is relatively easy, as compared with prior art assemblies, to fabricate and assemble.

In accordance with the invention there is provided a slipring assembly comprising male and female portions. The male portion is built up from a stack of wafers, or discs, of dielectric material and the female portion is built up from a stack of annular waferlike members of dielectric material. Each wafer, or disc, in the stack forming the male portion has an electrically conductive ring about the outer periphery thereof. Registered apertures in each wafer provide passageways or conduits for wires which are soldered to the various conductive rings on the wafers. Each annular waferlike member in the stack forming the female portion, which portion concentrically encompasses the male portion, carries a plurality of wires or contactors which make contact with the various conductive rings on the male portion. Registered apertures in the annular waferlike members provide passageways or conduits for wires which are electrically connected to the various wires or contactors on each annular waferlike member.

Other objects of the invention as well as the many features and advantages thereof will appear from an examination of the accompanying drawings together with the description, hereinafter set forth, of an embodiment which illustrates, but is not limitive of, the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal section of the lower part of a drill string showing the sliprings according to the invention as being incorporated in logging equipment within special subs in the drill string. 7

FIG. 2 is an enlarged cross-sectional view of the slipring as sembly of FIG. 1 in accordance with the subject invention.

FIG. 3 is an enlarged sectional view taken along the section line 3-3 in FIG. 2.

FIG. 4 is another enlarged sectional view taken along the section line 4P4 in FIG. 2.

FIG. 5 is still another enlarged cross-sectional view along the section line 5-5 in FIG. 2.

FIG. 6 is an enlarged perspective view, in exploded fonn, showing two consecutive female slipring assembly portions.

taken FIG. 7 is an enlarged exploded perspective view showing DESCRIPTION OF PREFERRED EMBODIMENT In the drawing, figures like elements or components are designated by the same reference numbers throughout. In FIG. 1 there is shown the lowermost section of a drill string which includes two subs 20 and 21 which, as illustrated, are threadably coupled end to end. Designated, generally, by the reference number 22 is a sealed capsule. The capsule 22 is a sealed container adapted to withstand pressures of about 14,000 pounds per square inch or more. As shown, the sealed capsule 22 is mounted coaxially within the special sub 20. Capsule 22 is welded to a long runner 39 which, in turn, is welded to sub 20. The special sub 24 in the illustration shown in FIG. 1, is a drill collar which has been hollowed out for the purpose of receiving the capsule 22.

Capsule 22 is comprised of a tubular member 23 of steel or another suitable high-strength material. Tubular member 23 is, as illustrated, internally threaded at its lower end. The aforementioned internal threads are for the purpose of receiving external threads formed on an end cap 24 or bull plug as it is often called. Bull plug 24 closes the lowermost end of the tubular member 23 of capsule 22. Bull plug 24 has formed therein on the outer surface thereof two annular recesses. These annular recesses are for the purpose of receiving the sealing O-rings 25 and 26.

Situated coaxially within tubular member 23 is a tubular container 27. Tubular container 27 houses a recorder and associated electrical circuitry. The recorder may, for example, be a multichannel magnetic tape recorder. As indicated in FIGS. 1 and 2, container 27 is mounted on a tapered rollerbearing structure designated, generally, by the reference number 28 so that the container 27 together with the contents which it houses can rotate thus avoiding damage to the contents during the borehole-drilling process, which process is usually attended by violent rotational forces.

Tubular container 27 has mounted at the upper end thereof another set of tapered roller bearings which are not illustrated in the drawing figures.

End cap 24, or bull plug, has at the lower end thereof an internally threaded aperture which receives the externally threaded end ofa conduit 29, as illustrated in FlG. 1. Conduit 29 carries therewithin a plurality of electric wires 5959 which ultimately enter the sealed capsule 22; or, more particularly, the tubular container 27 for interconnection with the recorder and its associated circuitry. As indicated, that end of conduit 2% which is in communication with the end cap 24 has formed in the outer surface thereof an annular groove. This groove is for the purpose of receiving a sealing O-ring 30. rings 25, 26 and 30 preserve the hermetic integrity of the capsule 22 and, more particularly, serve to prevent the entry of drilling fluid, or drilling mud as it is often called, from entering capsule 22. Drilling mud flows within the subs and 21 in the direction indicated by the labeled arrow (FIG. 11

The lowermost end of conduit 29 communicates with another sealed capsule designated, generally, by the reference number 33. Sealed capsule 31 contains circuitry for processing transducer signals. See, for example, the US. patent application hereinbefore referred to.

Sealed capsule 31 is similar to sealed capsule 22 and capsule 31 includes a tubular steel member 32 which has connected to the uppermost end thereof an end cap 33 or bull plug. End cap 33 is threadably engaged with the tubular member 32 as shown. In addition, end cap 33 has formed in the outer surface thereof two annular grooves for receiving the sealing O-rings 34 and 35.

Also, as indicated, the lowermost end of conduit 29 has formed therein two annular grooves for receiving two additional sealing O-rings 37 and 38. Thus, the O-rings 34, 35, 37 and 33 protect and hermetic the hermetic integrity of the sealed capsule 31.

Located within end cap 24 as shown in FIGS. I and 2 is the slipring assembly of the invention and it is designated,

generally, by the reference number 40. Slipring assembly is comprised of a female portion designated, generally, by the reference number 41 as well as a male portion which is designated, generally, by the reference number 42. As shown in FIG. 2 the female slipring portion 41 includes an annular dielectric spacer member 43 at its lower end and another annular dielectric spacer member 44 at its uppermost end. Between the annular spacer members 43 and 44 there is stacked, one on top of the other, a plurality of annular waferlike members 45, 46, 47, 48, 49, 50, 51 and 52. As indicated in FIGS. 1 through 5 the stack of annular waferlike members 45 through 52 concentrically encompasses the male slipring portion 42. The stack of waferlike members 45 through 52 forming the female sliping portion 41 are anchored within the end cap 24 and are immobile or static while the male slipring portion 42 is free to rotate.

As indicated in FIG. 2 the stack of annular waferlike members 45 through 52 is secured together by a plurality of long screws 53. The ends of the screws 53 are threadably received in holes provided in a steel disc 54 which, as shown, is located in the lower portion of the bull plug or end cap 24. Two annular grooves are provided in the periphery of the steel disc 54 and these grooves receive sealing O-rings 55 and 56.

An annular steel member 57, or retaining ring, which is radially split is provided at the uppermost end of the stack of waferlike members forming the female portion 41 in order to positively secure said female portion in its location in the end cap 24. As indicated in FIG. 2, the radially split annular member 57 is received in an annular groove provided in the internal surface of end cap 24.

As shown in FIG. 2, the steel disc 54 is provided with a plurality of apertures therethrough which receive a like plurality of electrical terminal members 58. Each terminal member 58 is exteriorly coated with a dielectric material. The dielectric outer coating on the electrical terminals 58 prevents an electrical connection between the terminals 58 and the steel disc 54.

As is indicated in FIG. 2, the male slipring portion 42 is comprised of a plurality of waferlike dielectric members or discs which are stacked serially in order to form the male slipring portion 42. More specifically, eight wafers, or discs, 60, 61, 62, 63, 64, 65, 66 and 67 are serially stacked and held together by a long screw 68 to form the male slipring portion 42.

The male slipring portion 42 is also comprised of a dielectric nose portion 69 as well as an elongated steel cylindrical portion 70 at the opposite end thereof. The cylindrical portion 70 having a smaller diameter portion 70a of dielectric material adjacent the annular spacer member 44 on the female slipring portion 41. The dielectric materials of which the annular members 45 through 52 and discs 60 through 67 are com prised of may, for example, be fiberglass impregnated with an epoxy material.

Also, as shown in FIG. 2, an additional screw 71 is used to secure the cylindrical portion 70 of the male slipring portion 42 to the tubular container 27.

FIGS. 3, 4 and 5 illustrate successive cross-sectional views through both the male and female slipring portions 41 and 42, as taken along the section lines 3-3, 4-4 and 55 (in FIG. 2) respectively.

As shown in FIGS. 3, 4 and 5 the annular waferlike members 45, 46 and 47 have a plurality of registering boltholes 72 therethrough. These boltholes 72 are for the purpose of receiving the long screws or bolts 53 (see FIG. 2). In addition, to the boltholes 72 there is provided in each of the annular waferlike members 45 through 52, inclusive, a circular groove 73 (see FIGS. 3-6). Moreover, as shown in FIGS. 3, 4 and 5 each groove 73 has a plurality of apertures 74 which pass transversely through each of the annular waferlike members. Also, as shown in FIGS. 3 through 6, there is situated within each of the circular grooves 73 in each annular waferlike member comprising the female slipring portion 41 an arcuate electrical conductor 75. Each arcuate conductor 75 is secured within groove 73 by being bonded therewithin by an epoxy compound. As indicated in FIGS. 3 through 6, each annular waferlilte member forming the female slipring portion 41 is provided with four longitudinal slots 76. Each of the slots 76 runs from the periphery of each annular waferlike member toward the large aperture in the center of each annular waferlike member. At the terminus of each slot 76 near the periphery of each annular waferlike member there is provided a recessed cavity 77. As shown in FIGS. 3-6, each annular waferlike member comprising the female slipring portion is provided with two pairs of flexible contact wires or brushes 78,78 and 79,79. Each of the contact wires 78,78 and each of contact wires 79,79 are, as indicated in FIG. 6, normally in parallel; the pair of contact wires 78 being substantially at right angles to the pair of contact wires 79. Each pair of contact wires 78 and 79 is cantilevered from each of the annular waferlike members with one terminus of each wire lying in one of the slots 76 and with an end of each of the contact wires being electrically bonded to the arcuate electrical conductor 75 by means of a silver solder connection 80. (see FIGS. 3-6) Each arcuate electrical conductor 75 and each pair of contact wires 78 and 79 are advantageously formed from gold alloy material. That portion of each of the contact wires which lies in its groove 76 is further secured by cementing each of the contact wires in such grooves by means of a hardenable epoxy compound, each groove 76 being filled with the epoxy compount to anchor the wires therein.

As shown in FIGS. 3, 4 and 5 each wafer or disc member 60 through 67 has secured to the outer periphery thereof a coin silver cylinder, or ring, 60a, 61a, 62a, 63a, 64a, 65a, 66a and 67a. Each of the wafers or discs including their coin silver cylinder comprising the male slipring portion 42 is assembled in the manner indicated in FIGS. 7 and 11. Each wafer or disc, 60 through 67, is stacked one upon the other with the long screw 68 passing through the large central aperture provided therein. The peripheral space between the adjacent coin silver tubes 60a, 61a, etc., is filled in with a hardenable epoxy compound which is ultimately machined so as to be flush with the outer surface of the coin silver rings, or cylinders. In FIG. 11 the filled-in hardenable epoxy compound is designated by the reference numbers 81.

As indicated in FIGS. 3, 4 and 5 each of the discs or wafers 60 through 67 is provided with a plurality of evenly spaced apertures therethrough. These apertures are designated by the reference number 82. Each aperture 82 of each adjacent wafer or disc is in registry. On each of the different wafers 60-67 terminating one of the apertures 82 and in electrical contact with the various coin silver cylinders 60a through 67a inclusive there is provided a terminating electrical contact 83.

Each electrical contact 83 is located at a different hole location 82 on each of the different discs 60 through 67 inclusive. Each hole or aperture 82 in each of the discs 60 through 67, inclusive, is in registration such that the aligned holes 82 form conduits running through the male portion 42 of the slipring assembly 40. Each of the aforementioned conduits contains a different insulated electrical conductor which ultimately runs through the aforementioned conduit through the male slipring portion 42 to the housing 27 containing the recorder and its associated circuitry whereat each of the conductors is appropriately connected to such circuitry as attends the recorder unit. As may be seen in FIG. 7 the disc 60 has one of its apertures 82 filled with a conductor 84 which conductor 84 is ultimately connected to an electrical contact 83 which is in electrical contact with the coin silver cylinder 60a on the disc 60. Similarly, the next adjacent disc 61 includes a different conductor 85 which passes through a different aperture 82 and is ultimately connected to a different electrical contact 83 which is in turn in contact with the coin silver cylinder 61a.

Returning again to FIGS. 3, 4, 5 and 6 whereat the annular waferlike members forming the female slipring portion 41 are shown, note that all of the apertures 74 are similarly in registration and also form conduits for various electrical conductors. For example, annular member 45 (FIG. 3) has a conductor 86 passing through one of its apertures 74 and this conductor 86 as shown in FIGS. 3 and 6 is connected via solder connector to the arcuate conductor 75. Similarly,, the next adjacent annular waferlike member 46 forming the female slipring portion 41 has a conductor 87 which passes through a different aperture 74 and, as indicated in FIG. 4, the conductor 87 runs in the groove 73 and is connected to the arcuate member 75 on the member 46 via the silver solder connection 80. A similar procedure is followed for the rest of the waferlike members forming the female slipring portion. For example, as shown in FIG. 5 the next waferlike member 47 has still a different conductor 88 passing through still a different aperture and the conductor 88 runs along the groove 73 and is ultimately connected in a similar manner to the arcuate conduc tor 75.

As is illustrated in FIG. 3 the spacing between each pair of contact wires 78 and 79 is indicated by the distance S and the diameter of the disc 60 including its contact cylinder 60a is D. The diameter D being larger than the distance S. The wire pair spacing S must be less than the diameter D and the ratio SID is such that the flexible contact wires 78 and 79 is just enough to prevent the contact wires from bouncing and thereby producing noise. As indicated in FIGS. 3,4 and 5, four points of contact between the contact wires and the coin silver cylinders are achieved. Also, the contact wires length is such that their free ends extend well beyond their points of contact with the rings 6011, etc.

Due to the small mass of the contact wires 78,78 and 79,79 which pairs are at substantially 90 angles with reference to each other, the noise due to vibration is at a minimum. With the wire contacts 90 apart at least one wire will always be in contact with the coin silver cylinders or rings even under conditions of radial vibration. Moreover, with the contact wires located as they are, the sliprings may be used as either static or rotating contacts; and, more importantly, rotation is possible in either direction (either clockwise or counterclockwise). Another advantage of the hereinbefore described slipring assembly is that the small size of the male portion of the slipring assembly allows the use of a more substantial support bearing in the instrumentation capsules. Another advantage is that the male and female portions may be easily engaged and disengaged. This is possible because the male and female portions can be joined by merely sliding one onto or into the other. Another advantage is that the use of a multiplicity of contact wires 78 and 79 allows the cancellation of noise from radial accelerations.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the inventive principles involves, it is to be understood that the invention may be embodied otherwise without departing from such principles. We claim:

1. In combination, first and second elongated hollow subs coupled end to end and adapted for incorporation in a drill string; first and second sealed capsules, the first capsule and second capsule being mounted within the first and second subs, respectively; said first and second capsules being longitudinally spaced apart; first and second end caps, each having a conduit-receiving aperture therethrough, the first end cap sealing one end of the first capsule and the second end cap sealing one end of the second capsule, said first and second end caps being in spaced-apart facing relationship, said first end cap having a cavity therein adapted to receive a slipring assembly; a first conduit extending between said end caps and terminating in the apertures thereof; a recording unit and associated circuitry arranged for rotation in the first capsule; transducer signals processing circuitry mounted in the second capsule; a slipring assembly including rotatable and stationary sub-assemblies mounted in the cavity in the first end cap; first electrical conductor means coupled to said recording unit and associated circuitry as well as to the rotatable subassembly of said slipring assembly; second electrical conductor means coupling said transducer signals processing circuitry and the stationary subassembly of said slipring assembly; said second electrical conductor means extending through the first conduit to effect the aforesaid coupling; the rotatable subassembly of said slipring assembly comprising a first body of dielectric material, a plurality of electrically conductive rings encompassing said first body and being afiixed thereto in spaced-apart relationship in series, said first body having a plurality of conduits formed therein, a plurality of electrical conductors each conductor being located in a different one of the last-mentioned conduits each of the last-mentioned conductors being connected with a different one of said conductive rings; the stationary sub assembly of said slipring assembly comprising a second body of dielectric material having a generally cylindrical space formed therein, said first body of said rotatable subassembly including the conductive rings on said first body being located in the cylindrical space of said second body, a plurality of first and second pairs of conductive wires mounted on said second body, one of said first and second pairs of wires of said plurality being in contact with one of said rings on said first body, said second body having a plurality of conduits therein, another plurality of electrical conductors, each conductor being located in a difi'erent one of the conduits in the second body and connected to a different first and second pair of wires of the plurality of conductive wires; the second electrical conductor means passing through said first conduit from the transducer signals processing circuitry and connected with the electrical conductors on said second body; whereby said first body of said rotatable subassembly of said slipring assembly is rotatable together with the recording unit and associated circuitry with respect to the transducer signals processing circuitry.

2. The combination according to claim 1 wherein each first pair of wires is arranged crosswise of each second pair of wires thereby providing four points of contact with each ring on said first body.

3. The combination according to claim 1 wherein said first body is comprised of a stack of discs and said second body is comprised of a stack of annular waferlike elements. 

1. In combination, first and second elongated hollow subs coupled end to end and adapted for incorporation in a drill string; first and second sealed capsules, the first capsule and second capsule being mounted within the first and second subs, respectively; said first and second capsules being longitudinally spaced apart; first and second end caps, each having a conduitreceiving aperture therethrough, the first end cap sealing one end of the first capsule and the second end cap sealing one end of the second capsule, said first and second end caps being in spaced-apart facing relationship, said first end cap having a cavity therein adapted to receive a slipring assembly; a first conduit extending between said end caps and terminating in the apertures thereof; a recording unit and associated circuitry arranged for rotation in the first capsule; transducer signals processing circuitry mounted in the second capsule; a slipring assembly including rotatable and stationary sub-assemblies mounted in the cavity in the first end cap; first electrical conductor means coupled to said recording unit and associated circuitry as well as to the rotatable subassembly of said slipring assembly; second electrical conductor means coupling said transducer signals processing circuitry and the stationary subassembly of said slipring assembly; said second electrical conductor means extending through the first conduit to effect the aforesaid coupling; the rotatable subassembly of said slipring assembly comprising a first body of dielectric material, a plurality of electrically conductive rings encompassing said first body and being affixed thereto in spaced-apart relationship in series, said first body having a plurality of conduits formed therein, a plurality of electrical conductors , each conductor being located in a different one of the last-mentioned conduits each of the last-mentioned conductors being connected with a different one of said conductive rings; the stationary sub assembly of said slipring assembly comprising a second body of dielectric material having a generally cylindrical space formed therein, said first body of said rotatable subassembly including the conductive rings on said first body being located in the cylindrical space of said second body, a plurality of first and second pairs of conductive wires mounted on said second body, one of said first and second pairs of wires of said plurality being in contact with one of said rings on said first body, said second body having a plurality of conduits therein, another plurality of electrical conductors, each conductor being located in a different one of the conduits in the second body and connected to a different first and second pair of wires of the pluraliTy of conductive wires; the second electrical conductor means passing through said first conduit from the transducer signals processing circuitry and connected with the electrical conductors on said second body; whereby said first body of said rotatable subassembly of said slipring assembly is rotatable together with the recording unit and associated circuitry with respect to the transducer signals processing circuitry.
 2. The combination according to claim 1 wherein each first pair of wires is arranged crosswise of each second pair of wires thereby providing four points of contact with each ring on said first body.
 3. The combination according to claim 1 wherein said first body is comprised of a stack of discs and said second body is comprised of a stack of annular waferlike elements. 